1. Field of the Invention
The present invention relates to an optical head of an optical disk apparatus, which processes information by applying a light beam to an optical disk for use as an information storage medium, and a lens actuator used in the optical head.
2. Description of the Related Art
An optical head of an optical disk apparatus comprises an objective lens which focuses a parallel laser beam, emitted from a semiconductor laser and guided through an optical system, including a collimator lens, a riser mirror, etc., onto an optical disk, and converts a reflected laser beam from the optical disk into a parallel beam again.
The objective lens is supported by means of a lens actuator having a lens holder, for movement in a direction (focus control direction) such that the lens moves toward and away from an information recording surface of the optical disk. Thus, the objective lens can be focused following fluctuations of the disk and the like.
Conventionally, the lens actuator of this type comprises a movable-side support member integral with the lens holder, a stationary-side support member located at a distance from the movable-side support member, and two parallel leaf springs, upper and lower, connecting these support members. The stationary-side support member is fixed to a carriage which is movable along the surface of the optical disk.
Meanwhile, optical heads of optical disk apparatuses are being reduced in size every year, and lens actuators for use therewith are also being miniaturized. The movable- and stationary-side support members and the upper and lower parallel leaf springs are formed by integral molding.
The lens actuators are molded in the following manner. After the two parallel leaf springs are positioned in a cavity of a mold, a resin is poured into the cavity. Then, the movable-side support member, with the lens holder thereon, and the stationary-side support member are molded. At the same time, fitting portions at the respective opposite ends of the leaf springs are embedded (or inserted) in the movable- and stationary-side support members, thereby forming an integral structure.
In the conventional lens actuators integrally molded in this manner, the two leaf springs of the same width are inserted in a manner such that they extend parallel to each other and overlap each other with respect to the planar direction.
Thus, in the conventional lens actuators, the insert-molded parallel leaf springs of the same width, upper and lower, overlap each other with respect to the planar direction (direction of the optical axis of the objective lens), so that molding the lens actuators requires use of complicated molds.
The mold comprises two basic components, i.e., an upper mold half and a lower mold half. The mold halves forms a cavity when they pare put together. In this cavity, the movable- and stationary-side support members will be molded. Demand has been made for a slide mold which is designed for use, along with the upper and lower mold halves, for molding parallel leaf springs, and which can be moved, after use, in a direction perpendicular to the direction in which the leaf springs overlap one another.
Thus, the molds used to form the lens actuators are complicated in construction and very expensive, so that the manufacturing cost of the lens actuators is high. Gaps is provided between each slide mold and the two leaf springs sandwiching the slide mode, to allow the slide molds to move without scratching the leaf springs. Due to these gaps, the leaf springs can move freely, inevitably decreasing the parallelism between them. That is, the leaf springs tilt in the clearance while the lens actuator are being formed. Consequently, crosstalks in the focusing and tracking directions are liable to be caused.
In addition to entailing the high manufacturing cost, as described above, the conventional lens actuators are subject to a drawback such that the mobility of the objective lens is not steady enough. Also, the optical heads which use these lens actuators have similar problems.